Modular brake pad

ABSTRACT

A modular brake pad is provided. The pad is made up of a brake backing plate and at least one pre-molded friction element. The friction element is releasably attached to the backing plate using an arrangement of guide rails. The friction element may also be locked to the plate by means of a releasable locking pin that extends through the plate into the friction element. An optional intermediary shim portion can also be provided on the friction element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to automotive brakes, and more particularly relates to brake pads for disc brake systems.

2. Description of the Related Art

The number of motor vehicles has increased greatly in recent years. There is an interest in methods of reducing the cost of manufacturing brakes and replacement parts on the part of both motor vehicle manufacturers and suppliers of parts for brakes. This increased use has also led to a significant increase in the after-market for brake replacement and repair. Brakes are also in increasing demand for motor vehicles such as airplanes, trains, bicycles, all terrain vehicles and motorcycles.

Brake pads, as currently manufactured, combine two main parts, namely a plate (often called a backing plate) and a friction pad. The brake pad is mounted in a brake assembly. The backing plate may be formed with a variety of bosses, holes, or other features for receiving and retaining the friction pad. The need to use high speed low cost manufacturing methods often results in irregularities in the plate which may lead to difficulties in attaching and/or retaining the friction pad on the plate during braking, when the friction pad is in contact with the rapidly turning brake rotor, or even during the pre-installation handling of the brake pad assembly.

There are a variety of known ways of attaching a friction pad to a plate. One such way is to attach the friction pad to the backing plate using rivets. One disadvantage of the riveting process is that it creates a rigid bond between the plate and the friction pad, which can, as a result of a sudden impact, lead to breaking of the friction pad. Furthermore, this process often requires one or more additional manufacturing steps with a consequent increase in cost. In addition, when the friction pad is worn down over time, the rivets become exposed and rub against the brake rotor, causing scoring on the rotor which is costly to repair.

Another, more recently developed method of mounting the friction pad on the plate is to use a pressurized molding process to mold the friction pad directly onto the plate. In this process, the friction pad may be prepared by blending the components of the friction pad into a pre-form or cake. A conventional pressurized molding system is used to mold the friction pad pre-form onto the plate. A layer of cement or glue is often applied to the contact surface of the plate to improve the adhesion between the plate and the friction pad.

As pressure is applied to the mold assembly, the pre-form becomes heated and begins to flow, filling the mold and covering the appropriate surface of the plate. In this process, the pre-form material is intended to flow into and around the various features to improve the bond between the plate and the friction pad.

The plate is subjected to a number of forces, such as the jarring of the moving vehicle, as well as vibration caused by the rotor and noise. The problem with the prior art processes and plates is that features, such as holes and bosses, stamped into the plate often provided insufficient shear and/or tensile strength in the bond between the friction pad and plate. When additional features are stamped into the plate to increase bond strength, additional manufacturing steps are required, adding to the cost.

The most common prior art features stamped into plates are circular holes. These holes often provide unsatisfactory results because, during the molding process, the pre-form cake does not completely fill all of the holes, which in turn, leads to deficient bonding between the plate and the pre-form. The incomplete hole fills are clearly visible, and often raise quality concerns when inspected by buyers. The incomplete hole fills also have an aesthetically displeasing appearance, which can also make them less attractive to customers. Accordingly, it has become common practice in prior art plates to fill the incomplete hole fills with putty and to paint over them, to both hide the unsatisfactory molding results and to improve appearance. These additional manufacturing steps have the added disadvantage of increasing the cost of manufacturing the disc brake.

Another concern that has become more pressing in the brake pad industry is the need for conservation, particularly of steel supplies, which have become more valuable. Brake backing plates, typically made of steel, are relatively durable and long-lasting, although the friction material attached to them is consumable. In the past, steel has been readily and cheaply available, and brake pads have been treated as a replaceable commodity (the entire unit being scrapped when the friction material is worn down). It would be desirable to preserve the backing plate portion for re-use (or re-cycling). It would be desirable to provide a modular brake pad that allows for installation and removal of replaceable friction elements, while ensuring a secure attachment with the backing plate.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a modular brake pad is provided. The pad has a brake backing plate (which has a friction surface and an opposing piston surface). At least one pair of raised guide rails is disposed on the friction surface. The pad also has at least one pre-molded friction element (which has a pair of opposing side edges). The edges are tapered for releasable engagement with the at least one pair of raised guide rails on the plate. In one embodiment, a locking pin extends through a bore in the plate and into a corresponding bore in the friction element to releasably lock the friction element to the plate. The friction element is removable from the plate by slideably disengaging the friction element from the guide rails. If locking pins are provided, these can be retracted to unlock the friction element from the plate before removal.

Preferably, the opposing side edges of the friction element are not parallel to each other. The friction element may have a trapezoidal shape, or any shape in which preferably the opposing side edges are disposed at an angle to each other.

The friction element may include an optional shim portion in addition to the friction material portion. The shim portion is releasably connected with the at least one pair of raised guide rails on the plate. The shim portion and friction material portion may be permanently connected to each other, or they may be separable.

Preferably, the shim portion is shaped to wrap around the friction material portion extending partway up the sides of the friction material portion. The upwardly extending side flanges on the shim portion may extend high enough (relative to the friction material) to serve as wear sensors.

Various configurations of the modular brake pad are possible. In one configuration, the pad has exactly two friction elements.

Preferably, the friction elements are different shapes on the right and left. They may be mirror image shapes of each other.

The friction elements may each have their own paired sets of guide rails. Alternatively, in one preferred embodiment, the plate has exactly three sets of guide rails, including a central guide rail(s) that holds both friction elements, and two outer guide rails that each grip a side edge of one of the friction elements.

Preferably, the at least one friction element is disengageable from the plate by sliding the friction element to disengage the side edges of the friction element from the guide rails.

Each guide rail may comprise a central post extending out from the plate and at least one overhanging lip extending out from the central post. The guide rails (particularly the central guide rails) may have two overhanging lips extending out left and right sides.

The guide rails may be integral with the plate, or may be separate pieces connected with the plate. In one embodiment, the guide rails are punched out from the plate.

Various configurations of locking pins are possible. Preferably, each locking pin has a conically shaped end for engaging the friction element. The locking pin can preferably be retracted by forcing a tool into the bore of the friction material to push the locking pin out through the piston side of the plate. Preferably, the locking pin is re-usable after retraction.

The backing plate may be made of any suitable hard material (especially metal or metal composite). In one possible embodiment, the backing plate is a steel backing plate.

Preferably, the piston surface of the plate is substantially flat (when the locking pin is in place if used). Preferably, the backing plate is substantially solid (i.e. having no holes apart from the bore for the locking pin). If no locking pin is used, the plate is preferably completely solid (having no holes whatsoever).

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIGS. 1, 2 and 3 show prior art brake pads for disc brake systems.

FIG. 4 is a front view of a backing plate according to the present invention.

FIG. 5 is a front view of the backing plate with optional shim portions for the removable friction elements.

FIG. 6 is a close-up view of a removable friction element showing friction material and shim portions.

FIG. 7 is a front disassembled view of the modular brake pad showing friction elements which can be slid into the guide rails for attachment to the backing plate.

FIG. 8 is a front assembled view of the modular brake pad showing friction elements engaged by the guide rails and attached to the backing plate.

FIG. 9 is a top assembled view of the modular brake pad showing friction elements engaged by the guide rails and attached to the backing plate.

FIG. 10 shows the piston side of the backing plate with locking pins engaged (i.e. locked position).

FIG. 11 shows the piston side of the backing plate with locking pins retracted (i.e. unlocked position).

FIG. 12 is a second front view of the backing plate with optional shim portions for the removable friction elements.

FIG. 13 is a detailed view of one possible configuration of the locking pins.

FIG. 14 is a piston side view of the modular brake pad showing locking pins engaged.

FIG. 15 is a detailed view of one embodiment of the shim portions of the friction elements (disassembled from the friction material portions).

FIG. 16 is a front assembled view of the modular brake pad showing friction elements engaged by the guide rails and attached to the backing plate.

FIG. 17 is a detailed view of one embodiment of the friction material portions of the friction elements (disassembled from the shim portions).

DETAILED DESCRIPTION

Brake pads for disc brake systems take the form of a two-piece assembly. The brake pads have a backing plate (a generally flat piece of thick metal) that is attached with a friction material (usually a metallic or ceramic composite). The friction material may be bonded or affixed to the backing plate in various ways. Prior art brake pads have been manufactured for permanent attachment between the friction material and the backing plate. Several examples of such brake pads are shown in FIGS. 1-3.

In the present modular brake pad, the friction material and backing plate are intended to be separable from each other (i.e. not permanently attached). This permits worn friction material elements to be swapped out for fresh friction material elements without the need to scrap the backing plate. Further, the modularity allows the brake pad to be customized--for example, to upgrade standard friction elements to a higher-performance category (e.g. for better thermal management, or noise reduction).

A sample backing plate 10 for the modular brake pad is shown in FIG. 4. The plate 10 has friction-40 and piston-facing 60 surfaces. The friction-facing surface 40 is shown in FIG. 4. On this side of the plate, guide rails 50 are disposed (in generally paired arrangements to connect with left and right sides of the replaceable friction elements). The guide rails 50 (which may be integral with the plate or separate hardware) are preferably configured to have a central vertical post portion 54 and one or more (preferably two) overhanging lips 52 that project slightly horizontally from the central post 54 to overhang and thus grip a side edge of the friction element 90 (gripping the shim portion 70 of the friction element 90, if provided). The guide rails, in a preferred embodiment, are punched out from the material of the backing plate (see punch wells 120 on FIGS. 10, 11 and 14), and the punched projections are then shaped by chisel or some other form of press tool) to divide the overhanging lips 52 from the central post 54 and force the lips to curl out (away from the central post).

A replaceable friction element 90 is shown in detail in FIG. 6. These friction elements are engageable with the backing plate on its friction side. As shown in FIGS. 7 and 8, the friction elements 90 are connected to the plate by sliding the friction elements into position on the friction side 40 of the plate. Side edges of the friction elements engage with guide rails 50 to prevent side-to-side and rotational shifting on the friction surface 40. To lock the friction elements with the backing plate, optional locking pins 20 may be forced into bores in the plate. The locking pins 20 extend into corresponding bores 120 in the friction elements to lock them to the plate. Locking pins 20 in locked and unlocked position are shown in FIGS. 10 and 11, respectively. Optionally, the modular brake pad may use no locking pins at all. The friction elements 90 are retained by the guide rails 50.

Each friction element 90 may itself be a two-part component. The friction element 90 may have a shim portion 70 and a friction material portion 100. As shown in FIGS. 6 and 17, the composite friction material may be pre-molded into a cake or a puck having tapered edges. A shim portion 70 of thin metal may be wrapped around the molded friction material in permanent or separable (nesting) arrangement. The shim portion preferably extends partway up at least two of the sides of the friction material portion. Side flanges 110 grip and protect the sides and bottom edges of the friction material (to prevent flaking, chipping and breakage of the material, particularly on the relatively thin wedge of the tapered bottom edge). The friction material is more crumbly and breakable than the shim portion 70. The shim 70 may also provide additional noise and vibration reduction in the overall brake pad. In one possible arrangement, the shim portions 70 may have additional gripping fingers or flanges 112 (see FIG. 15) at the top and/or bottom edges to further increase stability and prevent relative rotation between the friction material portion and the shim.

In one possible configuration, as shown in FIGS. 12 and 16, portions of the side flanges 110 of the shim may be configured to extend to a greater degree up the side wall of the friction material portion. In this way, these higher flanged portions 210 can serve as wear sensors for the pad. That is, as the friction material wears down (is consumed) in use of the brake, the portion 210 may become exposed and, by grating against the rotor, produce a sound that will alert the vehicle owner of the need to replace the friction elements on the brake pad.

One possible configuration of the locking pins 20 is shown in FIG. 13. The pins 20 may have a generally cylindrical body 24 with a flat base 26 and a conical (or frusto-conical) top portion 22. The conical shape is to aid in driving the pin into the relatively small diameter bore in the friction elements.

To drive the locking pins 20 into the assembly to hold the plate 10 and friction elements 90 together, the pins 20 are preferably punched, pressed or hammered from the piston-side 60 of the backing plate 10. The point 22 of the locking pin thus passes through the backing plate 10, through the shim portion 70 (via bore 80), and into the friction material portion 100. Preferably, the backing plate, shim portion and friction material portions are all pre-drilled (not necessarily together or at the same time) to have aligning bores to make a continuous channel through the assembly. The alignment of plate and shim bores is shown in FIGS. 5 and 12. As shown in FIG. 9, the friction material portion also has a bore 120 that can be accessed from the front (i.e. rotor-facing) surface of the friction material. This bore 120 is a smaller diameter bore than the bores in the plate and shim portion. Thus, the pin 20 has a frictional (or press-fit) engagement with the friction material inside the snug bore 120. Alternatively, no locking pins may be used and the plate and friction elements are solid with no bores whatsoever.

The pin 20 can be forced out of the bore 120 (and, in turn, out of the shim and backing plate) by poking a slender tool (not shown) into the bore 120 from the friction side and applying a sharp downward force to the tool to disengage the pin (for unlocking). The pin may be made to be re-used with a fresh friction element, or a new locking pin may be inserted.

The foregoing description illustrates only certain preferred embodiments of the invention. The invention is not limited to the foregoing examples. That is, persons skilled in the art will appreciate and understand that modifications and variations are, or will be, possible to utilize and carry out the teachings of the invention described herein. Accordingly, all suitable modifications, variations and equivalents may be resorted to, and such modifications, variations and equivalents are intended to fall within the scope of the invention as described and within the scope of the claims. 

1. A brake backing plate for a modular brake pad with pre-molded detachable friction elements, each friction element having an at least partially metallic shim portion and a friction material portion, the shim portion being shaped to wrap around the friction material portion and extend partway up the sides of the friction material portion, such that each friction element presents a pair of opposing side edges, the brake backing plate comprising: a substantially solid metallic body having a friction surface and an opposing piston surface, the plate having at least one pair of integral raised guide rails on the friction surface, each guide rail having a raised central portion with at least one outwardly extending overhanging lip, the lip being configured to receive a side edge of one of the friction elements so that the friction element is removable from the modular brake pad backing plate by slidably disengaging the friction element from the guide rails.
 2. The brake backing plate of claim 1, wherein the at least one pair of guide rails is configured to receive a friction element where opposing side edges of the friction element are not parallel to each other.
 3. The brake backing plate of claim 1, wherein the at least one pair of guide rails is configured to receive a friction element that has a trapezoidal shape.
 4. The brake backing plate of claim 1, wherein the at least one pair of guide rails is configured to receive a friction element where opposing side edges of the friction element are at an angle to each other.
 5. The brake backing plate of claim 1, having exactly two pairs of guide rails configured to receive two friction elements.
 6. The brake backing plate of claim 5, having exactly three guide rails, including a central guide rail that is part of both pairs of guide rails and grips a side edge of both friction elements, and two outer guide rails that each grip a side edge of one of the friction elements.
 7. The brake backing plate of claim 5, wherein the two pairs of guide rails are configured to receive two friction elements having different shapes.
 8. The brake backing plate of claim 5, wherein the two pairs of guide rails are configured to receive two friction elements that are right and left friction elements.
 9. The brake backing plate of claim 5, wherein the two pairs of guide rails are configured to receive two friction elements that are mirror image shapes of each other.
 10. The brake backing plate of claim 1, wherein the at least one friction element is disengageable from the plate by sliding the friction element to disengage the side edges of the shim portion from the guide rails.
 11. The brake backing plate of claim 1, wherein the guide rails are punched out from the plate.
 12. The brake backing plate of claim 1, wherein the backing plate is a steel backing plate.
 13. The brake backing plate of claim 1, wherein the piston surface of the plate is substantially flat.
 14. The brake backing plate of claim 1, further comprising at least on feature for receiving locking hardware for enabling locking at least one of the friction elements to the body of the backing plate, the locking hardware being removable from the plate to unlock the at least one friction element prior to slidably disengaging the friction element from the guide rails. 